Psychology in the tunnel

How people behave in case of emergencies

by
Julia Weiler

May 4, 2015

Mathematical models can help to determine the security level of tunnels. For instance, with simulations how fast a tunnel can be evacuated. Together with psychologists from Würzburg, RUB engineers investigate how people behave in case of emergencies in tunnels. Based on these data, they develop new evacuation models.

The danger in case of fire or explosions in tunnels derives not only from the fact that the structure may collapse, but also from the fact the people may possibly not be able to escape before smoke catches up with them. In Germany, there are laws in place that stipulate that a quantitative risk analysis has to be carried out for certain tunnels prior to their construction – e.g. very long ones or those that run under a body of water. Risk is calculated as the product of the extent of damage and the probability that a specific incident, such as a conflagration or a terrorist attack, may conceivably occur. In order to determine the extent of damage in case of fire, it is necessary, to put it simply, to calculate how quickly smoke would spread and how quickly people would be able to leave the tunnel. In the course of a project financed by the Federal Ministry of Education and Research (see also "Preventing terrorist attacks with shotcrete"), the RUB team assisted its partners from Würzburg University, the Federal Highway Research Institute and the “PTV Group” in the development of a model for numeric representation of tunnel evacuation.

“Ancient evacuation models from 1970s and 1980s still exist and are being applied for tunnels,” says RUB researcher Dr Götz Vollmann. These models are based on the assumption that people behave and move in a linear way, i.e. that they leave the tunnel directly and at a certain average speed in an emergency. But they do not, of course. Vollmann: “We know from the conflagrations in the Alp tunnels in the late 1990s, early 2000 that the reason many people died was not because they were exposed to fire, but simply because they did the wrong thing.” The only right thing to do when a hazardous situation arises in a tunnel is to drop everything and get to the next emergency tunnel. However, many people remain in their cars, because a car appears to be a relatively safe space.

Using a simulated accident, psychologists and engineers tested how people behave in an emergency in a tunnel.

Together with the Department of Psychology in Würzburg, headed by Prof Dr Paul Pauli, the RUB researchers analysed how people actually act in an emergency. They simulated an accident in the Engelbert-Tunnel in Gevelsberg (fig. 1). Seeing as this structure is closed every year for a funfair, it constituted an ideal test track. The team sent test participants in a test-car into the tunnel, who didn’t know what would happen inside. They came upon two heavy-duty vehicles that were wedged into one another. Using lights and stage smoke, the researchers set a dramatic scene. Cameras in the car and in the tunnel recorded the participants’ behaviour. How closely would people approach the accident? Would they stay in their car or try to escape? Would they make an emergency call? Would they attempt to extinguish the fire?

Data evaluation is still ongoing. Based on the results, the research group is setting up a computer model which reflects the diverse behaviours displayed by people in an emergency in a tunnel. They connect this model to a fluid dynamics model that simulates smoke movement. In future, scientists will thus be able to conduct much more realistic risk analysis for the evaluation of tunnels than ever before.

The team is also examining another aspect. The test participants were subdivided into three groups for the purpose of the experiment: one group had received a flyer issued by the Federal Highway Research Institute which recommends how to behave when facing a dangerous situation in a tunnel. Another group had studied the website of the Psychology Department in Würzburg, which provides detailed information regarding the correct behaviour in an emergency in tunnels. The last group had not received any information. The better informed a person was, the more likely they were to behave in the right way, i.e. leave the tunnel directly. This shows how important it is to spread information. The flyer issued by the Federal Highway Research Institute has been revised based on the results. The team from Würzburg is now planning to develop an app with detailed how-to regarding the behaviour in emergencies.

The fact that making the tunnel construction more secure is not enough is illustrated by another anecdote that Götz Vollmann knows about: following the fires in the Alp tunnels, millions of euros were invested in new security systems. Then, Smartphones were invented and social media took over. “Today, the first thing that people do when there’s a fire in a tunnel is pull out their phone and upload a photo to Facebook,” as the RUB researcher tells us. “Therefore, our work in the field of tunnel safety and security will probably never be done, because our society and our behaviour patterns are constantly changing.”

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